1. Field of the Invention
The present invention relates to a microwave oven having a silent cooking mode which can reduce noise generated when a user warms up food at night by adding the silent cooking mode to the microwave oven and a method for operating the microwave oven.
2. Description of the Prior Art
In general, a microwave oven warms up food by using microwaves.
When a door is either opened or shut by a user, a micro-switch of the microwave oven is operated according to the opening and shutting of the door. When the microswitch is operated, a magnetron generates the microwaves in response to a high voltage generated from a high voltage transformer. At this time, the heat generated from the magnetron of the microwave oven is cooled down by means of an external air inhaled from a fan motor of the microwave oven.
As described above, a cooking operation of the microwave oven is controlled by control apparatus installed in the microwave oven.
FIG. 1 is a block diagram for showing a circuit configuration of an apparatus for controlling a conventional microwave oven.
Referring to FIG. 1, the control apparatus of the microwave oven has a plug 10, a fuse 11, a temperature switch 12, a first switch 13, a control assembly 14, a second switch 17, contacts 15 and 16, a high voltage transformer 22, a high voltage rectifying section 23, a magnetron 24, a cooking chamber lamp 19, a tray motor 20, a fan motor 21, and a third switch 18. Control assembly 14 has a transformer 14a, and first and second relays 14b and 14c. High voltage rectifying section 23 has a high voltage diode 23a and a high voltage capacitor 23b.
When the user closes the door for cooking the food, first switch 13 and third switch 18 are turned on and second switch 17 is turned off.
Accordingly, a common alternating current source from plug 10 is applied to transformer 14a of control assembly 14 via fuse 11 and temperature switch 12. The common alternating current source of which the voltage is dropped to a predetermined voltage level by transformer 14a is applied to first relay 14b, second relay 14c, and a control section (not shown) as an operating current source, respectively.
At this time, when the user inputs a cooking start signal for cooking the food via a key input section (not shown), the control section excites first and second relays 14b and 14c in order to turn on the respective contacts 15 and 16 of first and second relays 14b and 14c.
Accordingly, the common alternating current source to which is applied via fuse 11 is applied to a primary winding of high voltage transformer 22 via first switch 13 and contact 15 of first relay 14b and is applied to cooking chamber lamp 19, tray motor 20, and fan motor via contact 16 of second relay 14c, respectively.
High voltage transformer 22 boosts a voltage of the common alternating current source applied via contact 15 of first relay 14b and plug 10. The boosted common alternating current source is converted into a direct current source by high voltage diode 23a and high voltage capacitor 23b of high voltage rectifying section 23 and is applied to magnetron 24.
Magnetron 24 generates the microwaves in response to the common alternating current source applied from high voltage rectifying section 23 and the food of the cooking chamber is cooked by the microwaves.
Meanwhile, cooking chamber lamp 19 emits light to the inside of the cooking chamber in response to the common alternating current source applied via contact 16 of second relay 14c and plug 10. Also, tray motor 20 rotates the tray on which the food is placed in response to the common alternating current source applied via contact 16 of second relay 14c and plug 10. Accordingly, the food which is put on the tray of the cooking chamber is uniformly cooked.
In addition, fan motor 21 is operated by the common alternating current source applied via contact 16 of second relay 14c and plug 10. Fan motor 21 inhales the external air for cooling the heat generated from high voltage transformer 22, magnetron 24, and the cooking chamber.
When the food put on the tray is cooked, the control section (not shown) turns off first and second relays 14b and 14c of control assembly 14. Accordingly, high voltage transformer 22, cooking chamber lamp 19, fan motor 21, and tray motor 20 are turned off.
Meanwhile, when the user opens the door while the food is cooked, the driving of magnetron 24 and of fan motor 21 is stopped by the opening of first switch 13 and of third switch 18. At this time, when first switch 13 is malfunctioned, the common alternating current source from plug 10 is not broken though the door is opened. However, in this case, since second switch 17 is turned on, the common alternating current source is broken.
As described above, in the prior microwave oven, when the food is cooked, cooking chamber lamp 19, tray motor 20, and fan motor 21 are simultaneously controlled by second relay 14b of control assembly 14.
Accordingly, when the microwave oven is operated, it is difficult to control an oscillating sound from magnetron 24 and a noise from fan motor 21. Particularly, in the night, since the noise from the fan motor 21 is loud, it's very difficult for the user to use the microwave oven.